A folding mobile telephone is generally has a structure in which an upper case is connected to a lower case via a hinge section so that the structure can be opened or closed. This structure can take two states of an open state and a close state. Thus, this structure has two advantages. One advantage is that a display screen can be increased by allowing the folding mobile telephone to be used while being opened. The other advantage is that the compact shape allows the mobile telephone in a close state to be carried easily.
A known conventional antenna for a folding portable wireless unit is disclosed in Japanese Patent Unexamined Publication No. 2001-156898 and Japanese Patent Unexamined Publication No. 2002-335180. In the conventional structure, an upper case includes therein an antenna element so that this antenna element is fed with power via a feeder passing through a hinge section. A lower case includes therein a ground pattern on a circuit board that functions as a lower antenna element.
However, in the above conventional folding portable wireless unit, antenna current flows in the entire lower case. Thus, this conventional structure has been involved with a problem in that the antenna performance deteriorates when the lower case in a calling state is gripped by a user.
Furthermore, main polarized wave according to an antenna radiation characteristic of the above conventional folding portable wireless unit flows in the longitudinal direction of the case. Thus, when the folding portable wireless unit in the calling state is retained while having an inclination, the main polarized wave is almost horizontal to ground surface. This has caused a problem in which the direction of the main polarized wave does not coincide with a generally vertical polarization wave from a base station antenna, thus causing deteriorated communication quality.
Furthermore, in a waiting state in which the structure having the upper case and the lower case is closed, the above conventional folding portable wireless unit is provided such that the antenna element in the upper case is in the vicinity of the circuit board of the lower case while the former is in parallel with the latter. This deteriorates the radiation resistance to deteriorate the antenna performance.